may,june11: pnt correction after platform leveling

26may11

Intro

Tilt sensor azswings were
done in early may11 to measure the residual platform tilt caused by the
platform beam repair. They showed that the platform was no
longer level (1 az term in the tilt data). A new tiedown setting was
computed from the tilt data to remove the tilt. Before these tiedown
changes could be installed, the pointing error caused by this
correction needs to be measured and included in then model.

Note: the pointing error from the gradual platform
tilt during the beam repair had been corrected by modifying the 1az
term of the pointing model (during the repair). These changes kept the
pointing error small, but the tilt still affected the gain of the
telescope as higher frequencies.
Starting on 15may11 pointing calibrations were done
(whenever an x111 rfi observation was available). The setup was:

Use sbh receiver.

move the tiedowns to the new positions to level the platform

Run the x102 calibration to measure any pointing error.

Move the tiedowns back to the standard position for regular
observing.